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Question Number 145163 Answers: 2 Comments: 0

Question Number 145162 Answers: 0 Comments: 1

we have z = e^(((2pi)/7)i) a = z+ z^2 + z^4 and b = z^3 + z^5 +z^6 we know a + b = −1 and 1−b=a find S = cos(((2pi)/7))+ cos(((4pi)/7)) + cos(((8pi)/7)) thanks for help

$${we}\:{have}\:{z}\:=\:{e}^{\frac{\mathrm{2}{pi}}{\mathrm{7}}{i}} \: \\ $$$${a}\:=\:{z}+\:{z}^{\mathrm{2}} \:+\:{z}^{\mathrm{4}} \:\:{and}\:{b}\:=\:{z}^{\mathrm{3}} \:+\:{z}^{\mathrm{5}} \:+{z}^{\mathrm{6}} \\ $$$${we}\:{know}\:\:{a}\:+\:{b}\:=\:−\mathrm{1}\:{and}\:\mathrm{1}−{b}={a} \\ $$$${find}\:{S}\:=\:{cos}\left(\frac{\mathrm{2}{pi}}{\mathrm{7}}\right)+\:{cos}\left(\frac{\mathrm{4}{pi}}{\mathrm{7}}\right)\:+\:{cos}\left(\frac{\mathrm{8}{pi}}{\mathrm{7}}\right) \\ $$$${thanks}\:{for}\:{help} \\ $$

Question Number 145174 Answers: 1 Comments: 0

Question Number 145193 Answers: 1 Comments: 1

Question Number 145191 Answers: 1 Comments: 0

if q≥1 and x>−1 then: (1+x)^q ≥ (1+x)^(q−1) + x ≥ 1+qx

$${if}\:\:{q}\geqslant\mathrm{1}\:\:{and}\:\:{x}>−\mathrm{1}\:\:{then}: \\ $$$$\left(\mathrm{1}+{x}\right)^{\boldsymbol{{q}}} \:\geqslant\:\left(\mathrm{1}+{x}\right)^{\boldsymbol{{q}}−\mathrm{1}} \:+\:{x}\:\geqslant\:\mathrm{1}+{qx} \\ $$

Question Number 145154 Answers: 0 Comments: 0

Question Number 145244 Answers: 0 Comments: 0

consider the circle (x−1)^2 +(y−1)^2 =2, A(1,4), B(1,−5). if P is a point on the circle such that PA+PB is maximum then prove that P,A,B are collinear points.

$$\mathrm{consider}\:\mathrm{the}\:\mathrm{circle}\: \\ $$$$\left(\mathrm{x}−\mathrm{1}\right)^{\mathrm{2}} +\left(\mathrm{y}−\mathrm{1}\right)^{\mathrm{2}} =\mathrm{2}, \\ $$$$\mathrm{A}\left(\mathrm{1},\mathrm{4}\right),\:\mathrm{B}\left(\mathrm{1},−\mathrm{5}\right).\:\mathrm{if}\:\mathrm{P}\:\mathrm{is}\: \\ $$$$\mathrm{a}\:\mathrm{point}\:\mathrm{on}\:\mathrm{the}\:\mathrm{circle}\:\mathrm{such}\:\mathrm{that} \\ $$$$\mathrm{PA}+\mathrm{PB}\:\mathrm{is}\:\mathrm{maximum}\:\mathrm{then} \\ $$$$\mathrm{prove}\:\mathrm{that}\:\mathrm{P},\mathrm{A},\mathrm{B}\:\mathrm{are}\:\mathrm{collinear}\: \\ $$$$\mathrm{points}. \\ $$

Question Number 145136 Answers: 1 Comments: 0

Soit X une variable aleatoire de loi geometrique de parametre p∈]0.1[ calculer P({X≥4})

$${Soit}\:{X}\:{une}\:{variable}\:{aleatoire}\:{de}\:{loi} \\ $$$$\left.{geometrique}\:{de}\:{parametre}\:{p}\in\right]\mathrm{0}.\mathrm{1}\left[\right. \\ $$$${calculer}\:{P}\left(\left\{{X}\geqslant\mathrm{4}\right\}\right) \\ $$

Question Number 145134 Answers: 0 Comments: 1

On dispose de N+1 urnes.l′urne U_k contient k boules blanches et N−k boules noires.on tire successivement sans remise n boules de l′urne et on note An l′evenement ′′choisir n boules noires lors des n premiers tirages′′. Determiner P(An). on notera U_k =′′choisir l′urne k′′

$${On}\:{dispose}\:{de}\:{N}+\mathrm{1}\:{urnes}.{l}'{urne}\:{U}_{{k}} \\ $$$${contient}\:{k}\:{boules}\:{blanches}\:{et}\:{N}−{k}\:{boules} \\ $$$${noires}.{on}\:{tire}\:{successivement}\:{sans}\: \\ $$$${remise}\:{n}\:{boules}\:{de}\:{l}'{urne}\:{et}\:{on}\:{note}\: \\ $$$${An}\:{l}'{evenement}\:''{choisir}\:{n}\:{boules}\:{noires} \\ $$$${lors}\:{des}\:{n}\:{premiers}\:{tirages}''.\:{Determiner} \\ $$$${P}\left({An}\right).\:{on}\:{notera}\:{U}_{{k}} =''{choisir}\:{l}'{urne}\:{k}'' \\ $$

Question Number 145137 Answers: 2 Comments: 3

Let a≥b≥c≥0 and a^2 +b^2 +c^2 = 3. Prove that a^3 +(b+c)^3 ≤ 9

$$\mathrm{Let}\:{a}\geqslant{b}\geqslant{c}\geqslant\mathrm{0}\:\mathrm{and}\:{a}^{\mathrm{2}} +{b}^{\mathrm{2}} +{c}^{\mathrm{2}} \:=\:\mathrm{3}.\:\mathrm{Prove}\:\mathrm{that} \\ $$$$\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:{a}^{\mathrm{3}} +\left({b}+{c}\right)^{\mathrm{3}} \:\leqslant\:\mathrm{9} \\ $$

Question Number 145129 Answers: 1 Comments: 0